This invention relates generally to the field of performing downhole functions in a well, and is particularly applicable to downhole well completion tools.
In completing a product recovery well, such as in the oil and gas industry, several downhole tasks or functions must generally be performed with tools lowered through the well pipe or casing. These tools may include, depending on the required tasks to be performed, perforating guns that ballistically produce holes in the well pipe wall to enable access to a target formation, bridge plug tools that install sealing plugs at a desired depth within the pipe, packer-setting tools that create a temporary seal about the tool and valves that are opened or closed.
Sometimes these tools are electrically operated and are lowered on a wireline, configured as a string of tools. Alternatively, the tools are tubing-conveyed, e.g. lowered into the well bore on the end of multiple joints of tubing or a long metal tube or pipe from a coil, and activated by pressurizing the interior of the tubing. Sometimes the tools are lowered on cables and activated by pressurizing the interior of the well pipe or casing. Other systems have also been employed.
Typically, ballistic tools are not xe2x80x9carmedxe2x80x9d (i.e., not yet configured to fire upon receipt of a hydraulic or electric stimulus) until just before being placed in the well, in order to avoid accidental firings at surface. Once armed, very high safety standards must be maintained to avoid potentially deadly premature firings until the tool is safely below ground. Even after the armed tool has been lowered into the well, an accidental, premature firing can result in costly well damage.
In one aspect of the invention, a downhole device for performing a function in a well has a series of dedicated hydro-mechanical locks that prevent occurrence of the function until desired. The hydro-mechanical locks are each capable of being released directly by a respective elevated hydraulic activating pressure condition and are constructed and arranged for sequential operation such that a lock in the series cannot be released until after the hydraulic pressure conditions required to release any preceding locks in the series have occurred.
In one embodiment, the device is in the form of a self-contained downhole device for controlling the occurrence of the function. In this embodiment, the device includes a downhole housing and a port in the housing in hydraulic communication with a remote hydraulic pressure source via the well by pressure-transmitting structure such as casing or tubing in the well.
In some embodiments, the series of hydro-mechanical locks comprises a set of one or more displaceable elements associated with a common hydraulic actuator, the actuator constructed and arranged to displace the elements sequentially. In some cases the actuator is responsive to an increase in hydraulic pressure to advance to engage an element and to a subsequent decrease in hydraulic pressure to move the element from a locking to an unlocking position.
Some preferred embodiments contain one or more of the following features: the actuator has a piston; the actuator is biased to a first position by a spring, the activating pressure condition moving the actuator to a second, activated position; the elements each comprises a ring, which in some embodiments is resiliently radially compressed, in a locking, unreleased condition, within a first bore of a lock housing; the actuator has a ring gripper for moving the ring; the lock housing has a second, larger bore into which the ring is movable to an unlocking, released position; the ring has an engageable cam surface; the gripper has a finger with a cam surface for engaging the cam surface of the ring, and in some instances a lift formation for lifting any previously released rings to enable the disengagement of an engaged ring from the cam surface of the gripper.
In some embodiments of the invention, the spring comprises a compressible fluid which is compressed in a first chamber by said actuator. In a particularly useful arrangement, the device also has an orifice for restricting a flow of the compressible fluid from the first chamber to a second chamber, enabling the respective activating pressure condition to cause the actuator to compress the fluid in the first chamber. In some instances the device has a third chamber and a floating piston disposed between the second and third chambers, the floating piston containing a one-way check valve constructed to enable flow from the second chamber to the third chamber. In this arrangement the construction of the floating piston advantageously enables oil within the first and second chambers to expand at higher temperatures.
In another embodiment, the series of hydro-mechanical locks comprises one or more valves, each valve arranged to be openable to a released condition in response to an activating hydraulic pressure condition. In a current arrangement, each of the valves has an inlet to receive activating pressure, and an outlet blocked from the inlet until after a respective activating pressure condition has occurred. In some arrangements, the outlet of the valve is hydraulically connected to an inlet of a pressure-activated tool.
In a particularly useful configuration, the valve is constructed to delay opening for a predetermined amount of time after the occurrence of a respective activating pressure condition. This delay time enables the inlet pressure condition to the valve to be reduced before the valve opens. In this manner, the opening of an upper valve in a series of valves does not immediately open a lower valve, enabling a series of such valves to be independently, sequentially opened by a sequence of activating pressure conditions.
Some configurations may have one or more of the following features: the valve has a piston that forces a fluid through an orifice to expose a port to open the valve; and the delay time between the occurrence of the respective activating pressure condition and the opening of the valve is determined at least in part by the size of the orifice.
In another aspect of the invention, a string of tools for performing downhole functions in a well includes a number of functional sections arranged in a physical order within the string along a string axis. At least one of the sections has a downhole device with a series of dedicated hydro-mechanical locks that prevent occurrence of an associated function. The hydro-mechanical locks are each capable of being released directly by a respective elevated hydraulic activating pressure condition, and are constructed and arranged for sequential operation such that a lock in the series cannot be released until after the hydraulic pressure condition required to release any preceding lock in the series has occurred.
In a particularly advantageous configuration, at least three of the sections each have such a device, the string being arranged and configured to perform the functions in an order other than the physical order of the sections along the axis.
In a preferred embodiment, the sections are constructed to enable activating pressure conditions to be applied simultaneously to all of the functional sections having the devices.
In some useful configurations, a first device in the string has at least one fewer dedicated hydro-mechanical locks than a second device in the string, the actuating pressure conditions for releasing the locks of the first and second devices being correlated such that pairs of locks of the first and the second devices are simultaneously released, resulting in all locks being released in the first device while a lock remains unreleased in the second device.
In another aspect of the invention, a downhole device for performing a function in a well has an actuator arranged to move along an axis in response to an activating pressure condition, an operator engageable by the actuator and arranged to cause the function to be performed when moved, and at least one lock element engageable by the actuator and disposed axially, in a locking position, between the actuator and the operator. The actuator is constructed and arranged to, in response to a first activating pressure condition, engage and move the lock element to a non-locking position, and subsequently, in response to a second activating pressure condition, to engage and move the operator to cause the function to be performed.
In a preferred embodiment, there are more than one lock element arranged in series between the actuator and the operator. In a preferred configuration, the axial motion of the actuator is limited by the lock element.
In another aspect of the invention, a method of performing a sequence of downhole functions in a well comprises lowering a string of tools, the string having a functional section associated with each function. At least two of the sections each has a device with a series of dedicated hydro-mechanical locks that prevent occurrence of the function associated with the section. The hydromechanical locks are capable of being released directly by a respective elevated hydraulic activating pressure condition, and are constructed and arranged for sequential operation, such that a lock in the series cannot be released until after the hydraulic pressure conditions required to release any preceding locks in the series have occurred.
The method also comprises applying a sequence of activating hydraulic pressure conditions to the string, a given activating pressure condition releasing an associated lock in predetermined functional sections having unreleased locks. The functional sections having the devices each perform their associated functions in response to an activating pressure condition occurring after all locks of the section have been released.
In some embodiments, at least one of the functional sections perforates the well in response to an activating pressure condition occurring after all locks within the section have been released.
In a particularly useful embodiment, the method includes maintaining the axial position of the string within the well while applying the sequence of activating pressure conditions to set a bridge plug at a first axial well position, set a packer at a second axial well position, and subsequently perforate the well between the first and second axial well positions.
In another embodiment, the method of the invention further includes maintaining the axial position of the string within the well while sequentially performing functions associated with at least three sections of the string. The sections include an upper section, a lower section, and at least one middle section, according to positions along an axis of the string. The method further includes performing the associated functions in an order starting with the function associated with a middle section.
In another embodiment, at least three of the sections are operated by the sequence of activating hydraulic pressure conditions to perforate upper, lower and middle well zones, the middle zone being perforated first.
In yet another useful embodiment, the method further comprises applying an elevated downhole test pressure. The test pressure releases an associated lock in each functional section having unreleased locks without causing any functional section to perform its associated function.
According to another aspect of the invention, a string of tools for performing a downhole function in a well includes a locking tool and a ballistic tool connected to the locking tool. The locking tool has a series of dedicated hydro-mechanical locks arranged to prevent arming of the ballistic tool, the locks capable of being released directly by a respective elevated hydraulic activating pressure condition. The locks are constructed and arranged for sequential operation, such that a lock in the series is not released until after the hydraulic pressure conditions required to release any preceding locks in the series have occurred, with the last released lock arranged to arm the ballistic tool when released.
In one embodiment, the ballistic tool is constructed to, once armed, delay performing the downhole function for a predetermined amount of time (preferably, between about 1 and 20 minutes) after the occurrence of a subsequent activating hydraulic pressure condition.
Preferably, the last released lock is constructed to, upon release, expose the ballistic tool to hydraulic pressure for receiving subsequent activating hydraulic pressure conditions.
The ballistic tool includes, in some configurations, a displaceable ballistic member and a target ballistic member. The last released lock is constructed to, upon release, enable the displaceable ballistic member to be hydraulically displaced toward the target ballistic member to arm the ballistic tool.
According to yet another aspect of the invention, a ballistic downhole tool is constructed to be armed downhole. The tool includes first and second ballistic components for transferring an internal detonation to fire the tool, the ballistic components initially being separated by a sufficient distance to inhibit the detonation transfer. The first ballistic component includes a piston. The tool also includes a lock arranged to retain the first ballistic component in its initial position, and a hydraulically activatable actuator adapted to release the lock to enable the first ballistic component to be moved toward the second ballistic component by hydraulic pressure acting against the piston, to arm the tool.
In some embodiments, the first ballistic component includes a firing pin and a length of detonator cord, the second ballistic component having a trigger charge arranged to be ignited by the detonator cord of the first ballistic component with the tool in an armed condition.
In the presently preferred embodiment, the first ballistic component also includes a release piston arranged to be moved by hydraulic pressure to release the firing pin.
The tool may also include a seal arranged to isolate the release piston from hydraulic pressure with the tool in an unarmed condition, to provide an additional safeguard against accidental firing.
Although surface accidents can generally be avoided by proper care and safety procedures, the invention can provide an additional level of safety by enabling the tool to be initially lowered into the well unarmed and subsequently armed only just before firing. Costly premature firings in the well can also be avoided. By keeping the ballistics unarmed while traversing the well, accidental firings caused by faulty seals and unexpected hydraulic conditions can also be avoided.
The invention advantageously enables functional tools to be arranged in a single downhole string in any desired physical order, and activated in any preselected sequence. This flexibility can be very useful, e.g. for perforating multiple zones in a well starting with a middle zone, or for perforating between a preset bridge plug and preset packer.
The invention also enables various arrangements of downhole tasks to be performed with a single string of tools, requiring only one trip down the well, thereby saving substantial rig time. Used in a triggering mechanism to trigger a detonation to activate a tool, the invention also advantageously avoids potential failure modes of electrically-activated downhole equipment and associated safety risks, by employing only hydro-mechanical downhole equipment for triggering detonations.
In embodiments in which the device according to the invention is employed to activate a tool, the activation of any of the tools in the string advantageously does not depend upon the previous activation of any other tools in the string, such that the failure of one tool to properly perform does not inhibit the operation of the other tools in the string.
These and other advantageous features are realized in equipment that is simple, reliable and relatively inexpensive.